fix cross-repo path deps; remove el compiler from neuron-lang/

- neuron-runtime, neuron-store, neuron-migrate: fix path deps
  (products/engram/ → foundation/engram/engrams/, products/el/ → foundation/el/engrams/)
- neuron-rs workspace: fix axon-events/axon-protocol paths
  (../../../platform/ → ../../platform/, paths were off by one level)
- neuron-lang/compiler/ removed (el self-hosting compiler now lives in foundation/el/el-compiler/)

Cargo.toml

@@ -5,13 +5,16 @@ members = [
     "crates/neuron-store",
     "crates/neuron-api",
     "crates/neuron-protocol",
-    "crates/axon-events",
     "crates/neuron-runtime",
     "crates/neuron-migrate",
     "crates/neuron-cli",
 ]
 
 [workspace.dependencies]
+# Platform-level Axon protocol crates (canonical source of truth)
+axon-events = { path = "../../platform/protocols/axon/crates/axon-events" }
+axon-protocol = { path = "../../platform/protocols/axon/crates/axon-protocol" }
+
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 uuid = { version = "1", features = ["v4", "serde"] }